Cut the beef across the grain into thin slices about 1/8-thick; cut those slices into 1-inch squares. Put the beef in a bowl, add the marinade, and toss lightly to coat. Cover with plastic wrap, and let the beef marinate for 1 hour at room temperature, or longer if possible in the refrigerator.
Heat a wok or large skillet, add 3 1/2 tablespoons of the oil, and heat until near smoking. Add the beef and stir-fry over high heat until it loses its raw color and the slices separate. Remove with a slotted spoon and drain. Clean out the pan.
Mix the ingredients for sauce together.
Reheat the pan, add the remaining 2 tablespoons oil, heat about 20 seconds, and add the garlic, ginger, and scallions. Cook for 20 seconds, until fragrant, then add the bean sprouts and toss lightly over high heat. Add the rice wine, and stir-fry for 1 1/2 minutes, then add the sauce and the cooked meat. Cook until the meat is heated through and everything is coated evenly with the sauce. Scoop the beef onto a serving platter and serve with rice and a vegetable, if desired.
Mix the ingredients for sauce together